Lead-coating process



' time to time. This method is suitable for lating billets for cold drawing or stamping Application filed April 15', 1920. Serial No. 374,089.

" v UNITED srmssf "Pinm m,-

ROBERT JAY SHOEMAKER, or .carcaco, ILLrNoIS, AssIGNoRTo LEADIZING- com.

; rm, orcmcneo nnmors, A CORPORATION or rumors.

'80 Drawing.

To all whom it concern v Be it known that I, ROBERT J. SHoEMnxER, a' citizen of. the Unlted States, residing at Chicago, in the county ofCook and State of Illinois, have invented certain new and useful Improvements in Lead-Coatingv Proo esses, of which the following is. a specification.-

'M invention relates to the operation of coating or plating articles made of iron or steel, with a lead plating; and the primary object of the invention is to provide an implating'metal which will be very'thin, so that the plating metal is not wasted, but at the 4 same time even, homogeneous and non-porous in character. Other incidental objects will be mentioned in connection with the following description of certain preferred methods of operation involving the principles of the invention.

The articles are immersed in a concentrated water solution of lead acetate, to which is preferably added a small amount of acetic acid. The solution may contain 50% v by weight of the lead acetate, 5% acetic acid,

and the balance water. 'The solution is heated to approximately 212 Fahrenheit, at

which temperature the lead acetate disassociates, producin deposition of the lead upon the surface to e plated. Iron acetate is formed which,under the influence of heat, is decomposed into ironhydrate and acetic acid. The iron hydrate will settle to the bottom of the tank and may be drained off. The solution .can be built up by adding new lead acetate crystals and acetic acid from 1n substitution for the common method of I the ordinary lubricant,

doping. The process as described to this point is not claimed herein as it forms-the subject matter" of an application filed December 11, 1920, Serial No. 429,889, as a condense and adheres firmly to the metal body'to which it is applied so that a billet for cold drawing, for example, may be drawn without use of it may nevertheless contain minute pores, (closed naturallyby the drawing process) but which if the article I Specification of Ietters Patent.

event, that the coating is when the article is removed from the bath.

LEAD-comma raocnss.

Patented Jan. 31,1922.

isnot subjected to further treatment by drawing otherwise may permit rusting through. To further increase this density of the plating the article is subjected to the following treatment:

The article is immersed in a fluid medium inert with respect to lead and heated to a temperature not below the melting point of lead, t h1s medlum consisting, preferably, of a h'quld or substance liquid at the temperature used and of a character to freely flow from the plated surface when the article is removed from the bath. I prefer to use a bath of zinc chloride to which 'common'salt is added, preferably in the proportions of 80% zinc'chloride and 20% sodium chloride which is heated to'approximately 650 Fahrenheit. For malleable iron castings, for example, or other iron or steel articles having a somewhat rough surface, I found it desirable to use a mixture of- 8 of zinc chloride, 15% of common salt and 5% of tin chloride.

At the temperature noted the lead plating dissolves superficially and flows with the re sult that'the plating is made homogeneous and non-porous. "Treatment in the bath of zinc chloride and common salt, or the bath .COIltfllIllIl'g the t1n chloride, will last about two or three minutes. The tin of e tin chloride, apparently, makes the dissolved lead more fluent and besides covers the lead plating witha thin film of lead, or alloys the lead plating with tin, the result being, in any made brighter and is. less affected by acids. The function of the common salt is to increase the fluidity of the bath in which the article is immersed so that the molten substance constituting the bath will'more freely flow off from the article coating will-be very thin so that the process may be used for plating threaded bolts or- J 'thelike since the plating metal will not fill up the threads.

I claim: i 1. 'Method of lead plating a metal article which consists in bringing the surface to be plated into contact with aconcentrated water solutlon of lead acetate heated to a temperature which will produce disassociation of the lead acetate and deposition of the lead on said surface, and then bringing the plated surface into contact with zinc chloride and common salt heated to a temperature which will superficially dissolve and produce a flow of the lead plating.

2. Method of lead plating a metal article which consists in bringing the surface to be plated into contact with a'concentrated water solution of lead acetate to produce depositure which will produce disassociation of the lead acetate and deposition of the lead on said surface, and then bringing the-plated surface into contact with a molten bath containing zinc chloride asa principal constituent to superficially dissolve and produce a flow of the lead plating.

4%. Method of lead plating a metal article which consists in bringing the stirface to be plated 1nto contact witha concentrated ater solution of lead acetate heatedto a temperature which will produce disassociation of the lead acetate and deposition of the lead on said surface and then bringing the plated surface into contact with a molten bath containing zinc chloride as a principal constituent and also tin chloride, for the purpose described.

p 5. Method of plating a metal article which consists in coating the same with a covering of lead and then bringing the coated surface into contact with a moltenbath containing tin chloride.

6. Method of plating a metal article which consists in coating the same'with a covering of lead and then bringing the coated surface into contact with a molten bath containing zinc chloride and tin chloride.

7. Method 'of plating a metal article that consists in coating the same with lead and then immersing the plated article in a fluid medium inert with respect to lead and heated tei a temperature not below the melting point 0 lead.

ROBERT JAY SHOEMAKERQ 

